Ion-exchange polymers

ABSTRACT

Ion-Exchange polymers for a polymer electrolyte membrane include a moiety of formula (I). and/or a moiety of formula (II), and/or a moiety of formula (III) wherein at least some of the units I, II and/or III are sulphonated; wherein the phenyl moieties in units I, II, and III are independently optionally substituted and optionally cross-linked; and wherein m, r, s, t, v, w and z independently represent zero or a positive integer, E and E′ independently represent an oxygen or a sulphur atom or a direct link, G represents an oxygen or sulphur atom, a direct link or a —O-Ph-O— moiety where Ph represents a phenyl group and Ar is selected from one of the above moieties (i) to (x) which is bonded via one or more of its phenyl moieties to adjacent moieties.

[0001] This invention relates to ion-exchange polymers and particularly,although not exclusively, relates to sulphonated polymers, for examplesulphonated polyaryletherketones, polyarylethersulphones and/orcopolymers of the aforesaid. Preferred embodiments of the inventionrelate to ion-conductive membranes, for example of polymer electrolytemembrane fuel cells, made using such polymers. The invention alsorelates to novel non-sulphonated polyaryletherketones and/orpolyarylethersulphones used for preparing said sulphonated polymers andprocesses for the preparation of polymers described herein.

[0002] A polymer electrolyte membrane fuel cell (PEMFC), shownschematically in FIG. 1 of the accompanying diagrammatic drawings, maycomprise a thin sheet 2 of a hydrogen-ion conducting Polymer ElectrolyteMembrane (PEM) sandwiched on both sides by a layer 4 of platinumcatalyst and an electrode 6. The layers 2, 4, 6 make up a MembraneElectrode Assembly (MEA) of less than 1 mm thickness.

[0003] In a PEMFC, hydrogen is introduced at the anode (fuel electrode)which results in the following electrochemical reaction:

Pt-Anode (Fuel Electrode) 2H₂→4H⁺+4e⁻

[0004] The hydrogen ions migrate through the conducting PEM to thecathode. Simultaneously, an oxidant is introduced at the cathode(oxidant electrode) where the following electrochemical reaction takesplace:

Pt-Cathode (Oxidant Electrode) O₂+4H⁺=4e ⁻→2H₂O

[0005] Thus, electrons and protons are consumed to produce water andheat. Connecting the two electrodes through an external circuit causesan electrical current to flow in the circuit and withdraw electricalpower from the cell.

[0006] U.S. Pat. No. 5,561,202 (Hoechst) discloses the production ofPEMs from sulphonated aromatic polyether ketones. At least 5% of thesulphonic groups in the sulphonic acid moieties are converted intosulphonyl chloride groups and then reacted with an amine containing atleast one cross-linkable substituent or a further functional group. Anaromatic sulphonamide is then isolated, dissolved in an organic solvent,converted into a film and then the cross-linkable substituents in thefilm are cross-linked. The invention is said to provide ion-conductivemembranes suitable for use as polymeric solid electrolytes which haveadequate chemical stability and can be produced from polymers which aresoluble in suitable solvents.

[0007] One problem associated with known PEMFCs is that of providingPEMs which have desirable properties at elevated temperatures and whichare cheap to manufacture.

[0008] It is an object of the present invention to address problemsassociated with PEMs.

[0009] According to a first aspect of the invention, there is provided apolymer electrolyte membrane which includes a polymer having a moiety offormula

[0010] and/or a moiety of formula

[0011] and/or a moiety of formula

[0012] wherein at least some of the units I, II and/or III aresulphonated; wherein the phenyl moieties in units I, II, and III areindependently optionally substituted and optionally cross-linked; andwherein m,r,s,t,v,w and z independently represent zero or a positiveinteger, E and E′ independently represent an oxygen or a sulphur atom ora direct link, G represents an oxygen or sulphur atom, a direct link ora —O-Ph-O— moiety where Ph represents a phenyl group and Ar is selectedfrom one of the following moieties (i) to (x) which is bonded via one ormore of its phenyl moieties to adjacent moieties

[0013] The invention extends to a polymer electrolyte membrane whichincludes a polymer having a moiety of formula I and/or a moiety offormula II and/or a moiety of formula III as described according to saidfirst aspect, wherein at least some of units I, II and/or III arefunctionalised to provide ion exchange sites. Suitably, to provide saidion exchange sites, said polymer is sulphonated, phosphorylated,carboxylated, quaternary-aminoalkylated or chloromethylated, andoptionally further modified to yield —CH₂PO₃H₂, —CH₂NR₃ ²⁰⁺ where R²⁰ isan alkyl, or —CH₂NAr₃ ^(x+) where Ar^(x) is an aromatic (arene), toprovide a cation or anion exchange membrane. Further still, the aromaticmoiety may contain a hydroxyl group which can be readily elaborated byexisting methods to generate —OSO₃H and —OPO₃H₂ cationic exchange siteson the polymer. Ion exchange sites of the type stated may be provided asdescribed in WO95/08581.

[0014] References to sulphonation include a reference to substitutionwith a group —SO₃M wherein M stands for one or more elements selectedwith due consideration to ionic valencies from the following group: H,NR₄ ^(y+), in which R^(y) stands for H, C₁-C₄ alkyl, or an alkali oralkaline earth metal or a metal of sub-group 8, preferably H, NR₄ ⁺, Na,K, Ca, Mg, Fe, and Pt. Preferably M represents H. Sulphonation of thetype stated may be provided as described in WO96/29360.

[0015] Unless otherwise stated in this specification, a phenyl moietymay have 1,4- or 1,3-, especially 1,4-, linkages to moieties to which itis bonded.

[0016] Said polymer may include more than one different type of repeatunit of formula I; more than one different type of repeat unit offormula II; and more than one different type of repeat unit of formulaIII.

[0017] Said moieties I, II and III are suitably repeat units. In thepolymer, units I, II and/or III are suitably bonded to one another—thatis, with no other atoms or groups being bonded between units I, II, andIII.

[0018] Where the phenyl moieties in units I, II or III are optionallysubstituted, they may be optionally substituted by one or more halogen,especially fluorine and chlorine, atoms or alkyl, cycloalkyl or phenylgroups. Preferred alkyl groups are C₁₋₁₀, especially C₁₋₄, alkyl groups.Preferred cycloalkyl groups include cyclohexyl and multicyclic groups,for example adamantyl. In some cases, the optional substituents may beused in the cross-linking of the polymer. For example, hydrocarbonoptional substituents may be functionalised, for example sulphonated, toallow a cross-linking reaction to take place. Preferably, said phenylmoieties are unsubstituted.

[0019] Another group of optional substituents of the phenyl moieties inunits I, II or III include alkyls, halogens, C_(y)F_(2y+1) where y is aninteger greater than zero, O—R^(q) (where R^(q) is selected from thegroup consisting of alkyls, perfluoralkyls and aryls), CF═CF₂, CN, NO₂and OH. Trifluormethylated phenyl moieties may be preferred in somecircumstances.

[0020] Where said polymer is cross-linked, it is suitably cross-linkedso as to improve its properties as a polymer electrolyte membrane, forexample to reduce its swellability in water. Any suitable means may beused to effect cross-linking. For example, where E represents a sulphuratom, cross-linking between polymer chains may be effected via sulphuratoms on respective chains. Alternatively, said polymer may becross-linked via sulphonamide bridges as described in U.S. Pat. No.5,561,202. A further alternative is to effect cross-linking as describedin EP-A-0008895.

[0021] However, for polymers according to the first aspect or secondaspect which are crystalline (which some are) there may be no need toeffect cross-linking to produce a material which can be used as apolymer electrolyte membrane. Such polymers may be easier to preparethan cross-linked polymers. Thus, said polymer of the first and/orsecond aspects may be crystalline. Preferably, said polymer is notoptionally cross-linked as described.

[0022] Where w and/or z is/are greater than zero, the respectivephenylene moieties may independently have 1,4- or 1,3-linkages to theother moieties in the repeat units of formulae II and/or III.Preferably, said phenylene moieties have 1,4-linkages.

[0023] Preferably, the polymeric chain of the polymer does not include a—S— moiety. Preferably, G represents a direct link.

[0024] Suitably, “a” represents the mole % of units of formula I in saidpolymer, suitably wherein each unit I is the same; “b” represents themole % of units of formula II in said polymer, suitably wherein eachunit II is the same; and “c” represents the mole % of units of formulaIII in said polymer, suitably wherein each unit III is the same.Preferably, a is in the range 45-100, more preferably in the range45-55, especially in the range 48-52. Preferably, the sum of b and c isin the range 0-55, more preferably in the range 45-55, especially in therange 48-52. Preferably, the ratio of a to the sum of b and c is in therange 0.9 to 1.1 and, more preferably, is about 1. Suitably, the sum ofa, b and c is at least 90, preferably at least 95, more preferably atleast 99, especially about 100. Preferably, said polymer consistsessentially of moieties I, II and/or III.

[0025] Said polymer may be a homopolymer having a repeat unit of generalformula

[0026] or a homopolymer having a repeat unit of general formula

[0027] or a random or block copolymer of at least two different units ofIV and/or V

[0028] wherein A, B, C and D independently represent 0 or 1 andE,E′,G,Ar,m,r,s,t,v,w and z are as described in any statement herein.

[0029] As an alternative to a polymer comprising units IV and/or Vdiscussed above, said polymer may be a homopolymer having a repeat unitof general formula

[0030] or a homopolymer having a repeat unit of general formula

[0031] or a random or block copolymer of at least two different units ofIV* and/or V*, wherein A, B, C, and D independently represent 0 or 1 andE, E′, G, Ar, m, r, s, t, v, w and z are as described in any statementherein.

[0032] Preferably, m is in the range 0-3, more preferably 0-2,especially 0-1. Preferably, r is in the range 0-3, more preferably 0-2,especially 0-1. Preferably t is in the range 0-3, more preferably 0-2,especially 0-1. Preferably, s is 0 or 1. Preferably v is 0 or 1.Preferably, w is 0 or 1. Preferably z is 0 or 1.

[0033] Preferably Ar is selected from the following moieties (xi) to(xxi):

[0034] Preferably, (xv) is selected from a 1,2-, 1,3-, or a 1,5-moiety;(xvi) is selected from a 1,6-, 2,3-, 2,6- or a 2,7-moiety; and (xvii) isselected from a 1,2-, 1,4-, 1,5-, 1,8- or a 2,6-moiety.

[0035] One preferred class of polymers may include at least some ketonemoieties in the polymeric chain. In such a preferred class, the polymerpreferably does not only include —O— and —SO₂— moieties between aryl (orother unsaturated) moieties in the polymeric chain. Thus, in this case,suitably, a polymer of the first and/or second aspects does not consistonly of moieties of formula III, but also includes moieties of formula Iand/or II.

[0036] One preferred class of polymers does not include any moieties offormula III, but suitably only includes moieties of formulae I and/orII. Where said polymer is a homopolymer or random or block copolymer asdescribed, said homopolymer or copolymer suitably includes a repeat unitof general formula IV. Such a polymer may, in some embodiments, notinclude any repeat unit of general formula V.

[0037] Referring to formula IV, preferably, said polymer is not apolymer wherein: Ar represents moiety (iv), E and E′ represent oxygenatoms, m represents zero, w represents 1, s represents zero, and A and Brepresent 1; Ar represents moiety (i), E and E′ represent oxygen atoms,G represents a direct link, m represents zero, w represents 1, rrepresents 0, s represents 1 and A and B represent 1; Ar representsmoiety (iv), E and E′ represent oxygen atoms, G represents a directlink, m represents 0, w represents 0, s represents 1, r represents 1 andA and B represent 1. Referring to formula V, preferably Ar representsmoiety (iv), E and E′ represent oxygen atoms, G represents a directlink, m represents zero, z represents 1, v represents zero and C and Drepresent 1.

[0038] Preferably, said polymer is not a sulphonated aromaticpolyetherketone of formula

-[[(Ph-O]_(p)-Ph-[[CO-Ph′]_(x)-O-Ph]_(h)-[CO-Ph′]_(y)-[O-Ph]_(n)-CO—]—

[0039] where Ph represents a 1,4- or 1,3-phenylene moiety; Ph′represents phenylene, naphthylene, biphenylene or anthrylene; p is 1, 2,3 or 4; x, h and n are, independently, zero or 1; and y is 1, 2 or 3.

[0040] Preferably, said polymer does not conform to the formula

[0041] where

[0042] e is from 0.2 to 1,

[0043] f is from 0 to 0.8, and

[0044] e+f=1

[0045] Preferably, said polymer does not conform to the formula

[0046] in which e is a number from 0 to 1, g is a number from 0 to 1, fis a number from 0 to 0.5, and the sum e+f+g=1.

[0047] Preferably, said polymer is not a copolymer built up from atleast two different units of formulae:

[0048] Suitable moieties Ar are moieties (i), (ii), (iv) and (v) and, ofthese, moieties (i), (ii) and (iv) are preferred. Preferred moieties Arare moieties (xi), (xii), (xiv), (xv) and (xvi) and, of these, moieties(xi), (xii) and (xiv) are especially preferred. Another preferred moietyis moiety (v), especially, moiety (xvi). In relation, in particular tothe alternative polymers comprising units IV* and/or V*, preferred Armoieties are (v) and, especially, (xvi).

[0049] Preferred polymers include an electron-rich, relativelynon-deactivated, easily sulphonatable unit, for example amulti-phenylene moiety or a fused-rings aromatic moiety, such asnaphthalene. Such an easy to sulphonate unit may be sulphonated underrelatively mild conditions to introduce two sulphonate groups per unit.Thus, preferred polymers may have at least 10π electrons in adelocalized aromatic moiety. The number of π electrons may be 12 orless. Preferred polymers include a biphenylene moiety. Other preferredpolymers include a naphthalene moiety. Preferred polymers include saidelectron rich, non-deactivated, easily sulphonatable unit bonded to twooxygen atoms. Especially preferred polymers include a—O-biphenylene-O-moiety. Other especially preferred polymers include a—O-naphthalene-O-moiety.

[0050] Preferred polymers include a first type of moiety which isrelatively difficult to sulphonate and a second type of moiety which isrelatively easy to sulphonate. For example, said second moiety may besulphonatable using the relatively mild method described in Example 13hereinafter, whereas the first moiety may be substantiallynon-sulphonatable in such a method. The use of the method of Example 13may be advantageous over currently used methods which use oleum. Apreferred second said moiety includes a moiety -Ph_(n)- wherein n is aninteger of at least 2. Said moiety is preferably bound to at least oneether oxygen. Especially preferred is the case wherein said moiety is—O-Ph-O— where said ether groups are para to the Ph-Ph bond.

[0051] Preferred polymers are copolymers comprising a first repeat unitwhich is selected from the following:

[0052] (a) a unit of formula IV wherein E and E′ represent oxygen atoms,G represents a direct link, Ar represents a moiety of structure (iv), mand s represent zero, w represents 1 and A and B represent 1;

[0053] (b) a unit of formula IV wherein E represents an oxygen atom, E′represents a direct link, Ar represents a moiety of structure (i), mrepresents zero, A represents 1, B represents zero;

[0054] (c) a unit of formula V wherein E and E′ represent oxygen atoms,G represents a direct link, Ar represents a moiety of structure (iv), mand v represent zero, z represents 1 and C and D represent 1;

[0055] (d) a unit of formula V wherein E represents an oxygen atom, E′represents a direct link, Ar represents a moiety of structure (ii), mrepresents 0, C represents 1, D represents 0; or

[0056] (e) a unit of formula V wherein E and E′ represents an oxygenatom, Ar represents a structure (i), m represents 0, C represents 1, Zrepresents 1, G represents a direct link, v represents 0 and Drepresents 1;

[0057] and a second repeat unit which is selected from the following:

[0058] (f) a unit of formula IV wherein E and E′ represent oxygen atoms,G represents a direct link, Ar represents a moiety of structure (iv), mrepresents 1, w represents 1, s represents zero, A and B represent 1;

[0059] (g) a unit of formula IV wherein E represents an oxygen atom, E′is a direct link, G represents a direct link, Ar represents a moiety ofstructure (iv), m and s represent zero, w represent 1, A and B represent1;

[0060] (h) a unit of formula V wherein E and E′ represent oxygen atoms,G represents a direct link, Ar represents a moiety of structure (iv), mrepresents 1, z represents 1, v represents 0, C and D represent 1; and

[0061] (i) a unit of formula V wherein E represents an oxygen atom, E′represents a direct link, G represents a direct link, Ar represents amoiety of structure (iv), m and v represent zero, z represents 1, C andD represent 1;

[0062] Other second units which may form copolymers with any of saidfirst repeat units (a) to (e) above include: a unit of formula IVwherein E and E′ represent oxygen atoms, G represents a direct link, Arrepresents a moiety of structure (v), m represents 0, w represents 1, srepresents 0, A and B represent 1; or a unit of formula V wherein E andE′ represent oxygen atoms, G represents a direct link, Ar represents amoiety of structure (v), m represents 0, z represents 1, v represents 0,C and D represent 1.

[0063] Preferred polymers for some situations may comprise first unitsselected from (a), (b), (c) and (e) and second units selected from (f),(g), (h) or (i). A polymer comprising units (d) and (h) may also bepreferred.

[0064] More preferred polymers are copolymers having a first repeat unitselected from those described above, especially repeat units (b), (d) or(e) in combination with a second repeat unit selected from units (f) or(h).

[0065] Preferred polymers having repeat unit(s) of formulae IV* and V*may include: a unit of formula IV* wherein Ar represents a moiety ofstructure (v), E represents a direct link, E′ represents an oxygen atom,G represents a direct link, w, s and m represent 0, A and B represent 1;and/or a repeat unit of formula V* wherein Ar represents a moiety ofstructure (v), E represents a direct link, E′ represents an oxygen atom,G represents a direct link, z, v and m represent 0, C and D represent 1.

[0066] Said polymers having repeat units IV* and V* may include any ofrepeat units (a) to (i) described above.

[0067] In some situations, polymers which include at least one repeatunit of formula IV or formula IV* may be preferred.

[0068] Copolymers may be prepared having one or more first repeat unitsand one or more of said second repeat units.

[0069] Where said polymer is a copolymer as described, the mole % ofco-monomer units, for example said first and second repeat unitsdescribed above, may be varied to vary the solubility of the polymer insolvents, for example in organic solvents which may be used in thepreparation of films and/or membranes from the polymers and/or in othersolvents, especially water.

[0070] Preferred polymers suitably have a solubility of at least 10%w/v, preferably a solubility in the range 10 to 30% w/v in a polaraprotic solvent, for example NMP, DMSO or DMF. Preferred polymers aresubstantially insoluble in boiling water.

[0071] First units of the type described above (with the exception ofunits (a) and (c)) may be relatively difficult to sulphonate, whereassecond units of the type described may be easier to sulphonate.

[0072] Where a phenyl moiety is sulphonated, it may only bemono-sulphonated. However, in some situations it may be possible toeffect bi- or multi-sulphonation.

[0073] In general terms, where a said polymer includes a —O-phenyl-O—moiety, up to 100 mole % of the phenyl moieties may be sulphonated.Where a said polymer includes a —O-biphenylene-O— moiety, up to 100 mole% of the phenyl moieties may be sulphonated. It is believed to bepossible to sulphonate relatively easily —O-(phenyl)_(n)-O— moietieswherein n is an integer, suitably 1-3, at up to 100 mole %.

[0074] Moieties of formula —O-(phenyl)_(n)-CO— or —O-(phenyl)_(n)-SO₂—may also be sulphonated at up to 100 mole % but more vigorous conditionsmay be required. Moieties of formulae —CO-(phenyl)_(n)-CO— and—SO2-(phenyl)_(n)-SO₂— are more difficult to sulphonate and may besulphonated to a level less than 100 mole % or not at all under somesulphonation conditions.

[0075] The glass transition temperature (T_(g)) of said polymer may beat least 144° C., suitably at least 150° C., preferably at least 154°C., more preferably at least 160° C., especially at least 164° C. Insome cases, the Tg may be at least 170° C., or at least 190° C. orgreater than 250° C. or even 300° C.

[0076] Said polymer may have an inherent viscosity (IV) of at least 0.1,suitably at least 0.3, preferably at least 0.4, more preferably at least0.6, especially at least 0.7 (which corresponds to a reduced viscosity(RV) of least 0.8) wherein RV is measured at 25° C. on a solution of thepolymer in concentrated sulphuric acid of density 1.84 gcm⁻³, saidsolution containing 1 g of polymer per 100 cm⁻³ of solution. IV ismeasured at 25° C. on a solution of polymer in concentrated sulphuricacid of density 1.84 gcm³, said solution containing 0.1 g of polymer per100 cm³ of solution.

[0077] The measurements of both RV and IV both suitably employ aviscometer having a solvent flow time of approximately 2 minutes.

[0078] The main peak of the melting endotherm (Tm) for said polymer (ifcrystalline) may be at least 300° C.

[0079] In general terms, said polymer is preferably substantially stablewhen used as a PEM in a fuel cell. Thus, it suitably has high resistanceto oxidation, reduction and hydrolysis and has very low permeability toreactants in the fuel cell. Preferably, however, it has a high protonconductivity. Furthermore, it suitably has high mechanical strength andis capable of being bonded to other components which make up a membraneelectrode assembly.

[0080] Said polymer may comprise a film, suitably having a thickness ofless than 1 mm, preferably less than 0.5 mm, more preferably less than0.1 mm, especially less than 0.05 mm. The film may have a thickness ofat least 5 μm.

[0081] Said polymer electrolyte membrane may comprise one or more layerswherein, suitably, at least one layer comprises a film of said polymer.Said membrane may have a thickness of at least 5 μm and, suitably, lessthan 1 mm, preferably less than 0.5 mm, more preferably less than 0.1mm, especially less than 0.05 mm.

[0082] The polymer electrolyte membrane may be a composite membranewhich suitably includes a support material for the conductive polymerfor importing mechanical strength and dimensional stability to themembrane. The polymer may be associated with the support material toform a composite membrane in a variety of ways. For example, anunsupported conductive polymer film can be preformed and laminated tothe support material. Alternatively, (and preferably) the supportmaterial may be porous and a solution of the conductive polymer can beimpregnated into the support material. In one embodiment, the supportmaterial may comprise, or preferably consist essentially of,polytetrafluoroethylene, suitably provided as a porous film. Such asupport material may be as described and used in accordance with theteachings of WO97/25369 and WO96/28242, the contents of which areincorporated herein by reference. Suitably, the support material has aporous microstructure of polymeric fibrils and is impregnated with saidpolymer throughout the material, preferably so as to render an interiorvolume of the membrane substantially occlusive.

[0083] The use of support material as described may allow polymers oflower equivalent weights (EW) (for example less than 500 g/mol, lessthan 450 g/mol or even less than 400 g/mol or 370 g/mol) or relativelyinflexible and/or brittle polymers to be used in polymer electrolytemembranes.

[0084] The polymer electrolyte membrane suitably includes a layer of acatalyst material, which may be a platinum catalyst (i.e. platinumcontaining) or a mixture of platinum and ruthenium, on both sides of thepolymer film. Electrodes may be provided outside the catalyst material.

[0085] It may be preferable for each phenyl group in a sulphonatedpolymer as described to be deactivated by being bonded directly to anelectron withdrawing group, for example a sulphonated group, a sulphonegroup or a ketone group.

[0086] According to a second aspect of the invention, there is provideda polymer electrolyte membrane which includes a polymer which includes:polyaryletherketone and/or polyarylethersulphone units; and units offormula —O-Ph_(n)-O— (XX) wherein Ph represents a phenyl group and nrepresents an integer of 2 or greater and wherein Ph groups of units(XX) are sulphonated.

[0087] Preferably, each phenyl group of moiety Ph_(n) is sulphonated,preferably mono-sulphonated. About 100 mole % of such phenyl groups maybe sulphonated as described.

[0088] Preferably, —OPhCO— and/or —OPhSO₂— moieties of said polymer aresulphonated to a lesser extent than the phenyl groups of moiety Ph_(n).Moieties —OPhCO— and —OPhSO₂— may be substantially non-sulphonated.

[0089] In one embodiment, said polymer may include no ketone linkagesand may have an equivalent weight of more than 900. Nonetheless, it hasbeen found, surprisingly, that such polymers are still conducting.

[0090] Said polymer electrolyte membrane may be for a fuel cell or anelectrolyser.

[0091] The invention extends to the use of a polymer which includesrelatively easy to sulphonate units and relatively difficult tosulphonate units in the preparation of a polymer for a polymerelectrolyte membrane.

[0092] The polymer electrolyte membrane described herein may include ablend of polymers, at least one of which is a polymer describedaccording to the invention described herein. Suitably the polymersdescribed herein are blended with 0-40 wt %, preferably 0-20 wt %, morepreferably 0-10 wt %, especially 0-5 wt % of other polymeric material.Preferably, however, a blend of polymers is not provided.

[0093] According to a third aspect of the invention, there is provided afuel cell or an electrolyser (especially a fuel cell) incorporating apolymer electrolyte membrane according to the first or second aspects.

[0094] According to a fourth aspect of the invention, there is providedany novel polymer as described according to said first aspect per se.

[0095] According to a fifth aspect of the invention, there is provided aprocess for the preparation of a polymer as described in the first,second, third and/or fourth aspects, the process comprising:

[0096] (a) polycondensing a compound of general formula

[0097] with itself wherein Y¹ represents a halogen atom or a group -EHand Y² represents a halogen atom or, if Y¹ represents a halogen atom, Y²represents a group E′H; or

[0098] (b) polycondensing a compound of general formula

[0099] with a compound of formula

[0100] and/or with a compound of formula

[0101] wherein Y¹ represents a halogen atom or a group -EH (or -E′H ifappropriate) and X¹ represents the other one of a halogen atom or group-EH (or -E′H if appropriate) and Y² represents a halogen atom or a group-E′H and X² represents the other one of a halogen atom or a group -E′H(or -EH if appropriate)

[0102] (c) optionally copolymerizing a product of a process as describedin paragraph (a) with a product of a process as described in paragraph(b);

[0103] wherein the phenyl moieties of units VI, VII and/or VIII areoptionally substituted; the compounds VI, VII and/or VIII are optionallysulphonated; and Ar, m, w, r, s, z, t, v, G, E and E′ are as describedabove except that E and E′ do not represent a direct link;

[0104] the process also optionally comprising sulphonating and/orcross-linking a product of the reaction described in paragraphs (a), (b)and/or (c) to prepare said polymer.

[0105] In some situations, the polymer prepared, more particularlyphenyl groups thereof, may be optionally substituted with the groupshereinabove described after polymer formation.

[0106] Preferably, where Y¹, Y², X¹ and/or X² represent a halogen,especially a fluorine, atom, an activating group, especially a carbonylor sulphone group, is arranged ortho- or para- to the halogen atom.

[0107] Advantageously, where it is desired to prepare a copolymercomprising a first repeat unit IV or V wherein E represent an oxygen orsulphur atom, Ar represents a moiety of structure (i), m representszero, E′ represents a direct link, A represents 1 and B represents zeroand a second repeat unit IV or V wherein E and E′ represent an oxygen orsulphur atom, Ar represents a moiety of structure (iv), m and wrepresent 1, G represents a direct link, s represents zero and A and Brepresent 1 wherein the polymer is not a random polymer but has aregular structure, the process described in paragraph (b) above may beused wherein in said compound of general formula VI, Y¹ and Y² represent—OH or —SH groups, Ar represents a moiety of structure (iv) and mrepresents 1 and in said compounds of general formulae VII and VIII, X¹and X² represent a fluorine atom, w,r,s,z,t and v represent 1 and Grepresents an oxygen or sulphur atom.

[0108] In another embodiment, where it is desired to prepare a copolymercomprising a first repeat unit IV or V wherein E and E′ represent anoxygen or sulphur atom, Ar represents a moiety of structure (iv), mrepresents zero, A represents 1, w represents 1, s represents zero and Brepresents 1 and a second repeat unit IV or V wherein E and E′ representan oxygen or sulphur atom, Ar represents a moiety of structure (iv), mand w represent 1, s represents zero and A and B represent 1, whereinthe polymer is not a random polymer but has a regular structure, theprocess described in paragraph (b) above may be used wherein in saidcompound of general formula VI, Y¹ and Y² represent —OH or —SH groups,Ar represents a moiety of structure (iv) and m represents 1 and in saidcompounds of general formulae VII and VIII, X¹ and X² represent afluorine atom, w,r,s,z,t and v represent 1 and G represents a —O-Ph-O—moiety.

[0109] Preferred halogen atoms are fluorine and chlorine atoms, withfluorine atoms being especially preferred. Preferably, halogen atoms arearranged meta- or para- to activating groups, especially carbonylgroups.

[0110] Where the process described in paragraph (a) is carried out,preferably one of Y¹ and Y² represents a fluorine atom and the otherrepresents an hydroxy group. More preferably in this case, Y¹ representsa fluorine atom and Y² represents an hydroxy group. Advantageously, theprocess described in paragraph (a) may be used when Ar represents amoiety of structure (i) and m represents 1.

[0111] When a process described in paragraph (b) is carried out,preferably, Y¹ and Y² each represent an hydroxy group. Preferably, X¹and X² each represent a halogen atom, suitably the same halogen atom.

[0112] Compounds of general formula VI, VII and VIII are commerciallyavailable (eg from Aldrich U.K.) and/or may be prepared by standardtechniques, generally involving Friedel-Crafts reactions, followed byappropriate derivatisation of functional groups. The preparations ofsome of the monomers described herein are described in P M Hergenrother,B J Jensen and S J Havens, Polymer 29, 358 (1988), H R Kricheldorf and UDelius, Macromolecules 22, 517 (1989) and P A Staniland, Bull, Soc,Chem, Belg., 98 (9-10), 667 (1989).

[0113] Where compounds VI, VII and/or VIII are sulphonated, compounds offormulas VI, VII and/or VIII which are not sulphonated may be preparedand such compounds may be sulphonated prior to said polycondensationreaction.

[0114] Sulphonation as described herein may be carried out inconcentrated sulphuric acid (suitably at least 96% w/w, preferably atleast 97% w/w, more preferably at least 98% w/w; and preferably lessthan 98.5% w/w) at an elevated temperature. For example, dried polymermay be contacted with sulphuric acid and heated with stirring at atemperature of greater than 40° C., preferably greater than 55° C., forat least one hour, preferably at least two hours, more preferably aboutthree hours. The desired product may be caused to precipitate, suitablyby contact with cooled water, and isolated by standard techniques.Sulphonation may also be effected as described in U.S. Pat. No.5,362,836 and/or EP0041780.

[0115] Where the process described in paragraph (b) is carried out,suitably, “a*” represents the mole % of compound VI used in the process;“b*” represents the mole % of compound VII used in the process; and “C*”represents the mole % of compound VIII used in the process.

[0116] Preferably, a* is in the range 45-55, especially in the range48-52. Preferably, the sum of b* and c* is in the range 45-55,especially in the range 48-52. Preferably, the sum of a*, b* and c* is100.

[0117] Where the process described in paragraph (b) is carried out,preferably, one of either the total mole % of halogen atoms or groups-EH/-E′H in compounds VI, VII and VIII is greater, for example by up to10%, especially up to 5%, than the total mole % of the other one ofeither the total mole % of halogen atoms or groups -EH/-E′H in compoundsVI, VII and VIII. Where the mole % of halogen atoms is greater, thepolymer may have halogen end groups and be more stable than when themole % of groups -EH/-E′H is greater in which case the polymer will have-EH/-E′H end groups. However, polymers having -EH/-E′H end groups may beadvantageously cross-linked.

[0118] The molecular weight of the polymer can also be controlled byusing an excess of halogen or hydroxy reactants. The excess maytypically be in the range 0.1 to 5.0 mole %. The polymerisation reactionmay be terminated by addition of one or more monofunctional reactants asend-cappers.

[0119] It is believed that certain polymers described herein are noveland, therefore, in a sixth aspect, the invention extends to any novelpolymer described herein per se.

[0120] It is also believed that certain polymers according to said firstand/or second aspect but which are not sulphonated are novel. Thus,according to a seventh aspect of the invention, there is provided anovel polymer having a moiety of formula I and/or a moiety of formula IIand/or a moiety of formula III wherein E,E′,G,m,r,s,t,v,w,z and Ar areas described in any statement herein.

[0121] Preferably, said polymer includes a moiety of formula II and/orIII and Ar is selected from

[0122] Preferably, in the aforementioned formulae, each —Ar— is bondedto adjacent moieties as described in any statement herein.

[0123] According to an eighth aspect of the invention, there is provideda process for the preparation of novel polymers according to saidseventh aspect, the process being as described according to the processof the fifth aspect except that compounds VI, VII and VIII are notsulphonated and the process does not include a sulphonation step.

[0124] Sulphonated polymers described herein may be made into filmsand/or membranes for use as PEMs by conventional techniques, for exampleas described in Examples 5 to 7 of U.S. Pat. No. 5,561,202.

[0125] The sulphonated polymers described herein may be used as polymerelectrolyte membranes in fuel cells or electrolysers as described.Additionally, they may be used in gas diffusion electrodes.

[0126] Any feature of any aspect of any invention or example describedherein may be combined with any feature of any aspect of any otherinvention or example described herein.

[0127] Specific embodiments of the invention will now be described, byway of example, with reference to FIG. 1 which is a schematicrepresentation of a polymer electrolyte membrane fuel cell.

[0128] As described above, the fuel cell includes a thin sheet 2 of ahydrogen-ion conducting Polymer Electrolyte Membrane. The preparation ofsheet material for such a membrane is described hereinafter.

EXAMPLE 1

[0129] A 700 ml flanged flask fitted with a ground glass Quickfit lid,stirrer/stirrer guide, nitrogen inlet and outlet was charged with4,4′-difluorobenzophenone (89.03 g, 0.408 mole),4,4′-dihydroxybenzophenone (34.28 g, 0.16 mole), 4,4′-dihydroxybiphenyl(44.69 g, 0.24 mole) and diphenysulphone (332 g) and purged withnitrogen for at least 1 hour. The contents were then heated under anitrogen blanket to between 140 and 145° C. to form an almost colourlesssolution. While maintaining a nitrogen blanket, dried sodium carbonate(43.24 g, 0.408 mole) was added. The temperature was raised gradually to335° C. over 200 minutes then maintained for 1 hour.

[0130] The reaction mixture was allowed to cool, milled and washed withacetone and water. The resulting polymer was dried in an air oven at120° C. The polymer had a Tg of 164° C., a melt viscosity at 400° C.,1000 sec⁻¹ of 0.48 kNsm⁻² and an inherent viscosity (IV) 0.40 (measuredat 25° C. on a solution of the polymer in concentrated sulphuric acid ofdensity 1.84 g.cm⁻³, said solution containing 0.1 g of polymer/100 cm³).

EXAMPLES 2 to 6

[0131] The polymerisation procedure of Example 1 was followed, exceptthat copolymers of different compositions were prepared by varying themole ratios of 4,4′-dihydroxybenzophenone to 4,4′-dihydroxybiphenyl,with the sum of the number of moles of the aforesaid reactants equallingthe number of moles of 4,4′-difluorobenzophenone, as described inExample 1. A summary of the mole ratios and the MV are detailed in thetable below. 4,4′ dihydroxybiphenyl: 4,4′- Example Nodihydroxybenzophenone MV (kNsm⁻²) 2 2:1 0.17  3a 1:1 0.48  3b* 1:1 0.694 1:2 0.54 5 1:3 0.43 6 1.25:1   0.34

EXAMPLE 7a

[0132] A 700 ml flanged flask fitted with a ground glass Quickfit lid,stirrer/stirrer guide, nitrogen inlet and outlet was charged with4,4′-difluorobenzophenone (89.03 g, 0.408 mole), 4,4′-dihydroxybiphenyl(37.24 g, 0.2 mole) 4,4′-dihydroxydiphenylsulphone (50.05 g, 0.2 mole),and diphenysulphone (332 g) and purged with nitrogen for over 1 hour.The contents were then heated under a nitrogen blanket to between 140and 150° C. to form an almost colourless solution. While maintaining anitrogen blanket, dried sodium carbonate (42.44 g, 0.4 mole) andpotassium carbonate (1.11 g, 0.008 mole) were added. The temperature wasraised gradually to 315° C. over 3 hours then maintained for 0.5 hours.

[0133] The reaction mixture was allowed to cool, milled and washed withacetone and water. The resulting polymer was dried in an air oven at120° C. The polymer had a Tg of 183° C., a melt viscosity at 400° C.,1000 sec⁻¹ of 0.78 kNsm⁻² and an inherent viscosity (IV) 0.40 (measuredat 25° C. on a solution of the polymer in concentrated sulphuric acid ofdensity 1.84 g.cm⁻³, the solution containing 0.1 g of polymer/100 cm³).

EXAMPLE 7b

[0134] The polymerisation procedure of Example 7a was followed exceptdried sodium carbonate (42.44 g, 0.4 mole) and dried potassium carbonate(1.11 g, 0.008 mole) was replaced by dried sodium carbonate only (43.24g, 0.408 mole). The polymer had a Tg of 183° C. and a melt viscosity at400° C., 1000 sec⁻¹ of 0.43 kNsm⁻²

EXAMPLES 8 and 10

[0135] The polymerisation procedure of Example 7b was followed, exceptthat copolymers were prepared by varying the mole ratios of thehydroxy-containing reactants, with the sum of the number of moles of theaforesaid equalling the number of moles of 4,4′-difluorobenzophenone. Asummary of the mole ratios and the MV are detailed in the table below.4,4′-dihydroxybiphenyl:4,4′- Example No dihydroxydiphenyl-sulphone MV(kNsm⁻²) 8 1:2 0.67 9 1:3 0.72 10   1:1.5 0.6

EXAMPLE 11

[0136] A 700 ml flanged flask fitted with a ground glass Quickfit lid,stirrer/stirrer guide, nitrogen inlet and outlet was charged with4,4′-dichlorodiphenylsulphone (104.25 g, 0.36 mole),4,4′-dihydroxydiphenylsulphone (6.75 g, 0.27 mole),4,4′-dihydroxybiphenyl (16.74 g, 0.09 mole) and diphenysulphone (245 g)and purged with nitrogen for at least 1 hour. The contents were thenheated under a nitrogen blanket to between 140 and 145° C. to form analmost colourless solution. While maintaining a nitrogen blanketpotassium carbonates (50.76 g, 0.37 mole) was added. The temperature wasraised to 180° C., held for 0.5 hours, raised to 205° C., held for 1hour, raised to 225° C., held for 2 hours, raised to 265° C., held for0.5 hours, raised to 280° C. and held for 2 hours.

[0137] The reaction mixture was allowed to cool, milled and washed withacetone/methanol (30/70) and water. The resulting polymer was dried inan air oven at 120° C.

EXAMPLE 12

[0138] The polymerisation procedure of Example 11 was followed, exceptthat the ratio of 4,4′-dihydroxybiphenyl to4,4′-dihydroxydiphenylsulphone was 1:2. The polymer has a Tg of 198° C.and on RV of 0.52.

EXAMPLE 13 Sulphonation of Polymers of Examples 1 to 12

[0139] The polymers of Examples 1 to 12 were sulphonated by stirringeach polymer in 98% sulphuric acid (3.84 g polymer/100 g sulphuric acid)for 21 hours at 50° C. Thereafter, the reaction solution was allowed todrip into stirred deionised water. Sulphonated polymer precipitated asfree-flowing beads. Recovery was by filtration, followed by washing withdeionised water until the pH was neutral and subsequent drying. Ingeneral, ¹H nmr in DMSO-d6 confirmed that 100 mole % of the biphenylunits had sulphonated, giving one sulphonic acid group, ortho to theether linkage, on each of the two aromatic rings comprising the biphenylunit. For examples 3 to 5, 100% sulphonation of —O-Ph-Ph-O— moieties wasconfirmed by converting the sulphonated ionomer from the H⁺ form to Na⁺form, by reacting 0.5 g of the dry sulphonated copolymer with an aqueoussolution of NaOH (2.5 g NaOH/200 ml water) at 60-65° C. for 2 hours thenwashing the product with water and drying at 60° C., followed by sodiumanalysis.

EXAMPLE 14 Membrane Fabrication

[0140] Membranes were produced from selected polymers of Examples 1 to12 after sulphonation as described in Example 13 by dissolvingrespective polymers in N-methylpyrrolidone (NMP). The polymers weredissolved at a concentration of 15% wt/v, except for Examples 3a and 6which were dissolved to 4% wt/v. The homogeneous solutions were castonto clean glass plates and then drawn down to give 300 micron films,using a stainless steel Gardner Knife. Evaporation at 100° C. undervacuum for 24 hours produced membranes of mean thickness 40 micronsexcept that Examples 3a and 6 produced membranes of about 10 microns.

EXAMPLE 15 Water-Uptake of the Membranes

[0141] 5 cm×5 cm×40 microns samples of membranes of Example 14 wereimmersed in deionized water (500 ml) for 3 days, dried quickly withlint-free paper to remove surface water and weighed, dried in an oven at50° C. for 1 day, allowed to cool to ambient temperature in a desiccatorthen weighed quickly.

[0142] The water uptake was measured as follows, with the results beingprovided in the table below. “Equivalent weight” is defined as theweight of polymer containing unit weight of replaceable acidic hydrogen.${\% \quad {Water}\quad {Up}\text{-}{take}} = {\frac{{{Wet}\quad {Weight}} - {{Dry}\quad {Weight}}}{{Dry}\quad {Weight}} \times 100}$

Membrane - prepared from Equivalent sulphonated polymer Weight % Waterof Example No: (g/mol) Up-take  2 360 136.4    3a 458 54.4  6 419 69.3   7a 476 61.5  8 690 30.5  9 904 21.9 10 583 38.7 11 976 21.6 12 74430.7

EXAMPLE 16 Performance of Membranes in a Polymer Electrolyte MembraneFuel Cell

[0143] The membranes prepared from sulphonated polymers of Examples 8 to11 were installed in a Standard PEMFC single cell test module andpolarisation date was generated and compared to Nafion 115, a leadingcommercially-available membrane. The current densities obtained at 0.8Vwere 0.42, 0.35, 0.58 and 0.26 Acm⁻² for the Example 8 to 11 polymersrespectively, compared to 0.12 Acm⁻² for Nafion 115.

EXAMPLE 17

[0144] The S number of a polymer is defined as follows:${S\quad {Number}} = \frac{{Number}\quad {of}\quad {unsulphonated}\quad {phenyls}}{{Number}\quad {of}\quad {sulphonated}\quad {phenyls}}$

[0145] The S number for polymers described above is summarised below.Example No. S Number 1 2.33 2 2 3 3 4 5 5 7 6 2.6  7a 3 8 5 9 7 10  411  7 12  5

EXAMPLE 18

[0146] A 500 ml, 3-necked round-bottomed flask fitted with a stirrer,nitrogen inlet and air condenser was charged with4,4′-difluorobenzophenone (35.79 g, 0.164 mole), hydroquinone (11.01 g,0.10 mole), 4,4′-dihydroxybiphenyl (18.62 g, 0.10 mole),4,4′-bis(4-chlorophenylsulphonyl)biphenyl (LCDC) (20.13 g, 0.04 mole)and diphenylsulphone (202.76 g) and the contents were heated under anitrogen blanket to 160° C. to form a nearly colourless solution. Whilemaintaining a nitrogen blanket, anhydrous potassium carbonate (29.02 g,0.21 mole) was added and the mixture stirred for 35 minutes. Thetemperature was raised gradually to 220° C. over 2 hours then raised to280° C. over 2 hours and maintained for 2 hours.

[0147] The reaction mixture was allowed to cool, milled and washed withacetone/methanol and water. The resulting solid polymer was dried at140° C. under vacuum. The polymer had a reduced viscosity of (RV) 2.50(measured at 25° C. on a solution of the polymer in concentratedsulphuric acid of density 1.84 g.cm⁻³, said solution containing 1 g ofpolymer/100 cm³) and a Tg of 186° C.

EXAMPLE 19

[0148] A 250 ml, 3-necked round-bottomed flask fitted with stirrer,nitrogen inlet and air condenser was charged with4,4′-difluorobenzophenone (33.06 g, 0.1515 mole), hydroquinone (13.21 g,0.12 mole), 9,9′-bis(4-hydroxyphenyl)fluorene(HPF) (10.512 g, 0.03mole), and diphenylsulphone (100.93 g) and the contents were heatedunder a nitrogen blanket to 150° C. to form a nearly colourlesssolution. While maintaining a nitrogen blanket, anhydrous potassiumcarbonate (21.77 g, 0.15751 mole) was added. The temperature was raisedto 175° C. maintained for 2 hours, raised to 200° C. maintained for 50minutes, raised to 250° C. maintained for 45 minutes, raised to 300° C.maintained for 90 minutes.

[0149] The reaction mixture was allowed to cool, milled and washed withacetone/methanol and water. The resulting solid polymer was dried at140° C. under vacuum. The polymer had an reduced viscosity (RV) of 0.76(measured at 25° C. on a solution of the polymer in concentratedsulphuric acid of density 1.84 g.cm⁻³, said solution containing 1 g ofpolymer/100 cm³) and a Tg of 165° C.

EXAMPLE 20

[0150] A 250 ml, 3-necked round-bottomed flask fitted with a stirrer,nitrogen inlet and air condenser was charged with4,4′-bis(4-chlorophenylsulphonyl)-terphenyl (23.2 g, 0.04 mole),4,4′-dihydroxybiphenyl (7.44 g, 0.040 mole) and diphenylsulphone (80 g)and the contents were heated under a nitrogen blanket to 170° C. to forma nearly colourless solution. While maintaining a nitrogen blanket,anhydrous potassium carbonate (5.64 g, 0.408 mole) was added. Thetemperature was raised to 200° C. and maintained for 30 minutes, raisedto 250° C. and maintained for 15 minutes, raised to 275° C. andmaintained for 15 minutes, raised to 330° C. and maintained for 1 hour.

[0151] The reaction mixture was allowed to cool, milled and washed withacetone/methanol and water. The resulting solid polymer was dried at140° C. under vacuum. The polymer had an inherent viscosity (IV) of 0.50(measured at 25° C. on a solution of the polymer in concentratedsulphuric acid of density 1.84 g.cm⁻³, said solution containing 0.1 g ofpolymer/100 cm³) and a Tg of 264° C.

EXAMPLE 21

[0152] A 250 ml, 3-necked round-bottomed flask fitted with a stirrer,nitrogen inlet and air condenser was charged with4,4′-difluorobenzophenone (21.82 g, 0.10 mole), 4,4′-dihydroxybiphenyl(18.62 g, 0.10 mole) and diphenylsulphone (60 g) and the contents wereheated under a nitrogen blanket to 180° C. to form a nearly colourlesssolution. While maintaining a nitrogen blanket anhydrous potassiumcarbonate (14.10 g, 0.102 mole) was added. The temperature was raised to200° C. over 60 minutes, raised to 250° C. maintained for 5 mins, raisedto 325° C. maintained for 5 mins, raised to 370° C. over 90 mins,maintained for 10 mins.

[0153] The reaction mixture was allowed to cool, milled and washed withacetone/methanol and water. The resulting solid polymer was dried at140° C. under vacuum. The polymer had an inherent viscosity (RV) of 1.28(measured at 25° C. on a solution of the polymer in concentratedsulphuric acid of density 1.84 g.cm⁻³, said solution containing 1 g ofpolymer/100 cm³) and a Tg 167° C.

EXAMPLE 22

[0154] A 250 ml, 3-necked round-bottomed flask fitted with a stirrer,nitrogen inlet and air condenser was charged with4,4′-difluorobenzophenone (22.04 g, 0.101 mole), 4,4′-dihydroxybiphenyl(6.52 g, 0.035 mole), hydroquinone (7.16 g, 0.065 mole) anddiphenylsulphone (60 g) and the contents were heated under a nitrogenblanket to 180° C. to form a nearly colourless solution. Whilemaintaining a nitrogen blanket anhydrous sodium carbonate (10.60 g,0.100 mole) and anhydrous potassium carbonate (0.28 g, 0.002 mole) wereadded. The temperature was raised to 200° C. held for 1 hour, raised to250° C. held for 1 hour, raised to 300° C. held for 1 hour. The reactionmixture was allowed to cool, milled and washed with acetone/methanol andwater. The resulting solid polymer was dried at 140° C. under vacuum.The polymer has an inherent viscosity (IV) 0.92 (measured at 25° C. on asolution of the polymer in concentrated sulphuric acid of density 1.84g.cm⁻³, said solution containing 0.1 g of polymer/100 cm³) and a Tg 156°C.

EXAMPLE 23

[0155] A 250 ml, 3-necked round-bottomed flask fitted with a stirrer,nitrogen inlet and air condenser was charged with4,4′-bis(4-fluorobenzoyl)diphenylether (21.34 g, 0.515 mole),4,4′-dihydroxybiphenyl (9.31 g, 0.050 mole) and diphenylsulphone (90 g)and the contents were heated under a nitrogen blanket to 160° C. to forma nearly colourless solution. While maintaining a nitrogen blanketanhydrous sodium carbonate (5.30 g, 0.050 mole) and anhydrous potassiumcarbonate (0.14 g, 0.001 mole) were added. The temperature was raised at1° C./min until it reached 345° C. and held for 1 hour.

[0156] The reaction mixture was allowed to cool, milled and washed withacetone/methanol and water. The resulting solid polymer was dried at140° C. under vacuum. The polymer had an inherent viscosity (RV) 1.48(measured at 25° C. on a solution of the polymer in concentratedsulphuric acid of density 1.84 g.cm⁻³, said solution containing 1 g ofpolymer/100 cm³) and a Tg 163° C.

EXAMPLE 24 General Procedure for Sulphonation of Polymers of Examples 18to 23

[0157] The polymers prepared as described in Examples 18 to 23 weresulphonated according to the following procedure.

[0158] The dried polymer was placed in a three-necked round-bottomedflask fitted with a stirrer containing 98% concentrated sulphuric acid(100 cm³), heated with stirring to 60° C. and maintained at thetemperature for 3 hours. The reaction product was poured into 5 litresof stirred ice/water mixture. The product precipitated out. It was thenfiltered-off, washed with iced-water until the pH was neutral, washedwith methanol and dried under vacuum at 100° C. The degree ofsulphonation was determined by elemental analysis, filtration or Nmr.

EXAMPLE 25 Sulphonation of Polymer of Example 22

[0159] The dried polymer from Example 22 (10 g) was placed in athree-necked round-bottomed flask fitted with a stirrer, containing 98%concentrated sulphuric acid (100 cm³), heated with stirring to 60° C.and maintained at that temperature for 3 hours. The reaction productswas poured into 5 litres of stirred ice/water mixture. The productprecipitated out, was filtered-off, washed with iced-water until the pHwas neutral, washed with methanol and dried under vacuum at 100° C. Nmranalysis showed the polymer had readily sulphonated, in which 95-100mole % of the ether-diphenyl-ether and ether-phenyl-ether units had beensulphonated.

EXAMPLE 26

[0160] A 500 ml 3-necked round bottomed quickfit flask fitted withstirrer/stirrer guide, nitrogen inlet and outlet was charged with4,4′-difluorobenzophenone (22.04 g, 0.102 mole),4,4′-dihydroxybenzophenone (10.71 g, 0.05 mole),2,7-dihydroxynaphthalene (8.01 g, 0.05 mole) and diphenyl sulphone (76.9g) and purged with nitrogen for at least 1 hour. The contents wereheated under a nitrogen blanket to about 132° C. to form a clearsolution. While maintaining a nitrogen blanket, dried sodium carbonate(10.81 g, 0.102 mole) was added. The temperature was raised gradually to290° C. over 240 minutes then maintained for 65 minutes.

[0161] The reaction mixture was allowed to cool, milled and washed withacetone and water. The resulting polymer had a Tg of 158° C. and meltviscosity at 400° C., 1000 sec⁻¹ of 0.5 kNsm⁻².

[0162] The polymer was sulphonated using the process described inExample 13. The resultant sulphonated polymer has a water-uptake of69.3% and an equivalent weight of 445.

[0163] The reader's attention is directed to all papers and documentswhich are filed concurrently with or previous to this specification inconnection with this application and which are open to public inspectionwith this specification, and the contents of all such papers anddocuments are incorporated herein by reference.

[0164] All of the features disclosed in this specification (includingany accompanying claims, abstract and drawings), and/or all of the stepsof any method or process so disclosed, may be combined in anycombination, except combinations where at least some of such featuresand/or steps are mutually exclusive.

[0165] Each feature disclosed in this specification (including anyaccompanying claims, abstract and drawings), may be replaced byalternative features serving the same, equivalent or similar purpose,unless expressly stated otherwise. Thus, unless expressly statedotherwise, each feature disclosed is one example only of a genericseries of equivalent or similar features.

[0166] The invention is not restricted to the details of the foregoingembodiment(s). The invention extends to any novel one, or any novelcombination, of the features disclosed in this specification (includingany accompanying claims, abstract and drawings), or to any novel one, orany novel combination, of the steps of any method or process sodisclosed.

1-35. (cancelled).
 36. A random or block copolymer comprising at leasttwo different units of general formula IV and/or V, wherein unit IV isof general formula

and unit V is of general formula

said copolymer including a first repeat unit selected from: (b) a unitof formula IV wherein E represents an oxygen atom, E′ represents adirect link, Ar represents a moiety of structure (i), m represents zero,A represents 1, B represents zero; (d) a unit of formula V wherein Erepresents an oxygen atom, E′ represents a direct link, Ar represents amoiety of structure (ii), m represents 0, C represents 1, D represents0; and (e) a unit of formula V wherein E and E′ represent an oxygenatom, Ar represents a structure (i), m represents 0, C represents 1, zrepresents 1, G represents a direct link, v represents 0 and Drepresents 1; and a second unit selected from: (f) a unit of formula IVwherein E and E′ represent oxygen atoms, G represents a direct link, Arrepresents a moiety of structure (iv), m represents 1, w represents 1, srepresents zero, A and B represent 1; and (h) a unit of formula Vwherein E and E′ represent oxygen atoms, G represents a direct link, Arrepresents a moiety of structure (iv), m represents 1, z represents 1, vrepresents 0, C and D represent
 1. 37. A copolymer according to claim 36which copolymer includes a first repeat unit comprising unit (b) and asecond repeat unit comprising unit (f); or said copolymer includes afirst repeat unit comprising unit (d) and a second repeat unitcomprising unit (f).
 38. A copolymer according to claim 37, wherein whenthe copolymer includes units (f) and (b), the ratio of the number ofmoles of unit (f) to the number of moles of unit (b) in the copolymer isin the range 1:6 to 1:1; and when the copolymer includes units (f) and(d), the ratio of the number of moles of unit (f) to the number of molesof unit (d) is in the range 1:1 to 1:3.
 39. A copolymer according toclaim 36 which includes units (f) and (b).
 40. A copolymer according toclaim 36 which includes units (f) and (d).
 41. A copolymer according toclaim 36, said copolymer having a glass transition temperature of atleast 144° C.
 42. A copolymer according to claim 36, said copolymerhaving a glass transition temperature of at least 154° C.
 43. Acopolymer according to claim 36, which has an inherent viscosity of atleast 0.3.
 44. A process for the preparation of a copolymer as describedin claim 36, the process comprising: (a) polycondensing a compound ofgeneral formula

with a compound of formula

and/or with a compound of formula

wherein Y¹ represents a halogen atom or a group -EH (or -E′H ifappropriate) and Y² represents a halogen atom or a group -E′H and X²represents the other one of a halogen atom or a group -E′H (or EH ifappropriate); wherein m, r, s, t, v, w and z independently represent 0or 1, E and E′ independently represent an oxygen atom, G represents adirect link and Ar is selected from a moiety of structure


45. A process according to claim 44, wherein Y¹ and Y² each represent anhydroxy group.
 46. A process according to claim 44, wherein X¹ and X²each represent a halogen atom.
 47. A process according to claim 46,wherein X¹ and X² each represent a fluorine atom.
 48. A processaccording to claim 44, wherein “a*” represents the mole % of compound VIused in the process; “b*” represents the mole % of compound VII used inthe process; and “c*” represents the mole % of compound VIII used in theprocess; and wherein a* is in the range 45-55.
 49. A process accordingto claim 48, wherein the sum of b* and c* is in the range 45-55.
 50. Aprocess according to claim 48, wherein the sum of a*, b* and c* is 100.51. A process according to claim 44, wherein one of either the totalmole % of halogen atoms or groups -EH/-E′H in compound VI, VII and VIIIis greater than the total mole % of the other one of either halogenatoms or groups -EH/-E′H in compounds VI, VII and VIII.
 52. A processaccording to claim 44, which includes controlling the molecular weightof the copolymer by using an excess of halogen or hydroxyl reactants.53. A process according to claim 44, wherein a copolymer which includesunits (f) and (b) or which includes units (f) and (d) is prepared in thepresence of sodium carbonate; or sodium carbonate and potassiumcarbonate.